Suggestions for configuring inputs for XBLA/PSN/PC/Mac

So, I'm not going to lie, I'm not the most experienced with the inputs manager. I'm getting there with the help of the manual and a lot of googling... But this is a rather specific question that I'd like to know about.

Here's the (hopeful) scenario: I want to make a twin-stick shmup game BUUT... I want to give it PC/Mac support with the second stick being the mouse instead... BUUT... I also want to give it game-pad support for the main consoles and PC/Mac (MotionInJoy is already installed and configured so I can test.)

Also... Say for the console ports, what if I want it to be multiplayer offline? (as in, up to four players sitting on the couch.) I gather how I would go about setting that all up but the main focus is.

... When making the game can I put into the input manager an eventuality for all of these possible scenarios? Would it even be able to handle that?

I am aware that it'd likely be more sensible to make a port for each system when I get to that point... But hey, I thought I may as well ask if this is do-able (whether it's wise or not is another discussion entirely. )